Magnetic sensor and scanning microscope

ABSTRACT

An object of the present invention is to provide a magnetic sensor simply configured so as to magnetically measure not only conductive materials but also nonconductive materials over a wide temperature range and which offers high performance and high reliability, as well as a scanning microscope that uses the magnetic sensor. A scanning microscope according to the present invention includes a magnetic sensor with a magnetic sensing element provided at a free end of a cantilever-like flexible member and a strain gauge installed on the flexible member, driving means for driving the flexible member or a measurement sample, and control means for controlling driving provided by the driving means based on an output signal from the strain gauge.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/665,613, which was filed on Feb. 12, 2010, as a national-stageapplication of PCT/JP2008/056058, which was filed on Mar. 28, 2008. Eachof the above-referenced applications is incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present invention relates to a magnetic sensor and a scanningmicroscope that uses the magnetic sensor.

BACKGROUND ART

A scanning probe microscope (SPM: Scanning Probe Microscopy) is anapparatus configured to measure and map the surface structure andphysical properties of a measurement sample. Depending on the physicalproperties to be measured, various scanning probe microscopes have beendeveloped, such as scanning tunneling microscopes (STM: ScanningTunneling Microscope) and atomic force microscopes (AFM). In particular,a scanning Hall probe microscope (SHPM: Scanning Hall Probe Microscopy)is a measuring apparatus that is useful for quantitatively and directlyobserving magnetic domains; the scanning Hall probe microscope isconfigured to detect leakage magnetic fields from a magnetic material ora magnetic medium and to measure the physical quantity distribution ofmagnetic properties of the leaking magnetic fields and display thedistribution as an image. Known scanning probe microscopes are describedin, for example, Non-Patent Document 1 and Patent Document 1.

-   [Non-Patent Document 1] “Real-time scanning Hall probe microscopy,”    Appl. Phys. Lett, 69, pp. 1324-1326, (1996)-   [Patent Document 1] Japanese Patent Laid-Open No. 2004-226292

The conventional scanning Hall probe microscope described in Non-PatentDocument 1 uses a Hall probe including an STM chip and a Hall elementintegrated together to perform magnetic imaging measurement. The Hallprobe is fixed to the leading end of a tube-like piezoelectric (PZT)actuator. The Hall probe is kept in proximity to the surface of ameasurement sample until a tunnel current starts to flow between the STMchip and the measurement sample. A feedback circuit in the Hall probemonitors the tunnel current. Thus, the Hall probe kept at a givendistance from the measurement sample (lift mode) scans the surface ofthe measurement sample.

However, the measurement using the Hall probe with the STM chip asdescribed above is limited to measurement samples with conductivesurfaces. Furthermore, a complicated electronic circuit is required tomonitor the tunnel current. Moreover, since the Hall probe is separatedfrom the surface of the measurement sample, it is difficult to achievemeasurement at a sufficiently high sensitivity and a sufficiently highspatial resolution using weaker magnetism. Additionally, the Hall probefixed to the piezoelectric actuator floats at a short distance (forexample, several nm) from the surface of the measurement sample. Thus,upon undergoing a certain external impact during measurement, the Hallprobe may come into contact (interfere) with the measurement sample. Asa result, one or both of the Hall probe and the measurement sample maybe damaged accidentally or over time.

Furthermore, the Hall probe is swung along the surface of themeasurement sample using the portion thereof fixed to the piezoelectricactuator as a support point, to subject the surface of the measurementsample to fine (micromotion) scanning. Thus, a gradual increase in swingangle progressively increases the distance between the Hall probe andthe measurement sample. This reduces the resolution of measurementimages in the scanning direction, making the images blurred. Moreover, ahigh voltage required to control the piezoelectric actuator may inducespurious noise and the like.

Moreover, to allow the vortex state of a superconductive material or thelike to be observed, the measurement sample and the Hall probe need tobe cooled to a liquid helium temperature. However, the tube-likepiezoelectric actuator offers a very narrow displacement range at suchvery low temperature, thus limiting the scan range of the Hall probe toabout 1 μm×1 μm. This prevents the measurement sample from beingobserved over a wide range. To solve this problem, the present inventorshave proposed a configuration in which the piezoelectric elementdescribed in Patent Document 1 is installed in a room temperatureenvironment. The present inventors have thus successfully applied thescanning Hall probe microscope to very low temperature. However, thisapparatus has a slightly complicated configuration and requires anincreased installation area for the members thereof. Thus, there hasbeen a demand for a further reduction in the scale of the apparatus.

SUMMARY

The present invention has been developed in view of the above-describedcircumstances. An object of the present invention is to provide amagnetic sensor simply configured so as to magnetically measure not onlyconductive materials but also nonconductive materials over a widetemperature range and which offers high performance and highreliability, as well as a scanning microscope that uses the magneticsensor.

To accomplish the above-described object, a magnetic sensor comprises acantilever-like flexible member, a magnetic sensing element provided ata free end of the flexible member, and a strain gauge provided on atleast a part of the flexible member.

In the magnetic sensor configured as described above, when the magneticsensing element comes into abutting contact with the surface of themeasurement sample, the flexible member shaped like a cantilever bows toreduce the pressing force of the magnetic sensing element applied to thesurface of the measurement sample. In conjunction with this, the straingauge provided on at least a part of the flexible member (for example,on the surface of the flexible member if the flexible member is shapedlike a plate) is deformed to provide a detection signal (for example, anoutput voltage obtained when an input voltage is applied to a bridgecircuit). Then, the detection signal is monitored to allow detection ofthe bowing of the flexible member, that is, the abutment contact betweenthe magnetic sensing element and the measurement sample. Magneticmeasurement is performed with the magnetic sensing element in abuttingcontact with the measurement sample. This eliminates the need for an ATMchip provided on the conventional Hall probe. Furthermore, the magneticsensor offers improved sensitivity, and eliminates the need formicromotion control required for the conventional piezoelectricactuator.

Furthermore, the type of the magnetic sensing element is notparticularly limited. The magnetic sensing element is, for example, aHall element or a magnetoresistive element. In view of theabove-described conventional problems, the present invention isparticularly useful when the magnetic sensing element is a Hall element.

Moreover, to be more reliably inhibited from being damaged upon cominginto contact with the measurement sample, the magnetic sensing elementmay be coated with a protective film. In this case, the protective filmmay be thin enough to be prevented from reducing the sensitivity of themagnetic sensing element. Furthermore, the protective film usefully hasa higher “hardness” than a material for the magnetic sensing element toprovide a sufficient protective function for the magnetic sensingelement, and may have a lower “hardness” than the measurement sample inorder to protect the measurement sample. The “hardness” may be comparedin terms of any of indentation hardness, scratch hardness, and reboundhardness. Examples of such hardness include Brinell hardness, Vickershardness, Knoop hardness, Rockwell hardness, superficial hardness, Meierhardness, durometer hardness, Barcol hardness, Mnotron hardness, Martenshardness, and Shore hardness.

Moreover, a material for the flexible member is not limited; theflexible member may be formed of, for example, resin. For example, thecantilever-like member has a monolithic structure integrated withmagnetic sensing element. In this case, the cantilever-like memberrequires micromachining technique. Furthermore, if the magnetic sensingelement has a multilayer structure, the cantilever-like member may bedifficult to process. In contrast, resins are inexpensive materials thatare easy to handle and process. There are many types of resin, and theflexibility and environment resistance of the resin can be easily set byappropriately adjusting the type or thickness of the resin.

Furthermore, a scanning microscope according to the present invention iseffectively configured using the magnetic sensor according to thepresent invention. The scanning microscope comprises a cantilever-likeflexible member, a magnetic sensing element provided at a free end ofthe flexible member, a strain gauge provided on at least a part of theflexible member, driving means for driving the flexible member or ameasurement sample, and control means for controlling driving providedby the driving means based on an output signal from the strain gauge.Furthermore, the magnetic sensing element is usefully a Hall element. Atleast an area of the magnetic sensing element which comes into contactwith the measurement sample may be coated with a protective film. Theflexible member may be formed of, for example, a resin. In addition, thedriving section (means) may be of a non-piezoelectric element type.Moreover, the control means may control the driving means so that themagnetic sensing element and the measurement sample are adjustablybrought into abutting contact with each other or separated from eachother, based on an output signal from the strain gauge.

ADVANTAGE OF THE INVENTION

The magnetic sensor and scanning microscope according to the presentinvention enable not only conductive materials but also nonconductivematerials to be magnetically detected and eliminate the need for anactuator that uses a piezoelectric element or the like to drive themagnetic sensor, allowing the apparatus configuration of the apparatusto be simplified. Furthermore, the scan range at very low temperaturecan be sufficiently increased, enabling magnetic measurement over a widetemperature range. Moreover, sensitive magnetic detection can beachieved with the sensor in contact with or in close proximity to themeasurement sample. As a result, the magnetic measurement performanceand reliability of the sensor and apparatus can be drastically improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing the configuration ofan embodiment of a magnetic sensor according to the present invention;

FIG. 2 is a plan view schematically showing the configuration of theembodiment of the magnetic sensor according to the present invention;

FIG. 3 is an enlarged schematic plan view showing a part of theembodiment of the magnetic sensor according to the present invention;

FIG. 4 is a circuit diagram showing an example of a bridge circuitconfigured to measure a variation in the resistance of a strain gauge;

FIG. 5 is a schematic diagram showing the configuration of an embodimentof a scanning microscope according to the present invention;

FIG. 6 is a two-dimensionally visualized image obtained by measuring themagnetic domains on the surface of a thin iron garnet film using anexample of the scanning microscope according to the present invention;

FIG. 7 is a two-dimensionally visualized image obtained by measuring themagnetic domains on the surface of the thin iron garnet film using theexample of the scanning microscope according to the present invention;and

FIG. 8 is a two-dimensionally visualized image obtained by measuring themagnetic domains on the surface of the thin iron garnet film using theexample of the scanning microscope according to the present invention.

DETAILED DESCRIPTION

An embodiment of the present invention will be described below. The sameelements are denoted by the same reference numerals, and duplicatedescriptions are omitted. Furthermore, positional relations in theup-down direction, the lateral direction, and the like are based onthose shown in the drawings unless otherwise specified. Moreover, thedimensional ratio is not limited to those shown in the drawings.Additionally, the embodiment described below only illustrates thepresent invention and is not intended to limit the present inventionthereto. Moreover, the present invention can be varied without departingfrom the spirit thereof.

FIGS. 1 and 2 are a perspective view and a plan view schematicallyshowing an embodiment of a magnetic sensor according to the presentinvention. FIG. 3 is a partly enlarged schematic plan view of a part ofthe magnetic sensor.

The magnetic sensor 1 includes a Hall element section 12 (magneticsensing element) located at one end of a resin plate 11 (flexiblemember) that appears to be rectangular in a plan view; the Hall elementsection 12 appears to be generally rectangular in a plan view andincludes a plurality of probes 12 a formed substantially like radiallyarranged strips of paper. The Hall element section 12 includes, forexample, an active area of about several μm×several μm. The Hall elementsection 12 is manufactured by forming a two-dimensional electron gas(2DEG) AlGaAs/InGaAs hetero structure on a GaAs substrate by epitaxialgrowth in which the vapor phase of an organic metal material is used asa material gas, and processing the hetero structure into a desired shapeby photolithography.

Furthermore, the Hall element section 12 is covered with a protectivefilm (not shown in the drawings) that protects both the Hall elementsection 12 and the surface Sa of a measurement sample S (describedbelow) that comes into contact with the Hall element section 12. Thetype and material of the protective film are not particularly limited.For example, the protective film is harder (has a higher “hardness”)than the material for the Hall element section 12, and is softer (has alower “hardness”) than the surface Sa of the measurement sample S interms of protection of the surface Sa. More specifically, an example ofthe protective film is an organic nitride such as silicon nitride. Thethickness of the protective film is also not particularly limited; theprotective film is, for example, a thin film having a thickness of about50 nm in order to prevent a decrease in the magnetic detectionsensitivity of the Hall element section 12.

Moreover, each of the probes 12 a of the Hall element section 12 haswires 16 formed of Au or the like and connected to the base end thereofvia respective electrode pads 16 a formed of Au or the like. Each of thewires 16 is stuck to the surface of the resin plate 11 and extendedunder a strain gauge 14 described below to a terminal 16 b on a base 13.If the joint strength between the resin plate 11 and the wires 16 isinsufficient, the wires 16 and/or electrode pads 16 a may be formed of,for example, a conductive medium such as conductive paste which containsconductor colloids.

Furthermore, the resin plate 11 is formed of a resin film such aspolyimide resin and is thus flexible. An end of the resin plate 11 whichis opposite the end including the Hall element section 12 is fixed tothe base 13, which is thicker than the resin plate 11. That is, theresin plate 11 is shaped like a cantilever such that the end at whichthe Hall element section 12 is fixed functions as a free end, whereasthe end fixed to the base 13 functions as a fixed end.

Moreover, a thin film-like strain gauge 14 is installed so as to extendfrom a central portion of the resin plate 11 onto the base 13. An I/Ogauge lead 17 is connected to the base of a resistor grid 14 a of thestrain gauge 14. The strain gauge 14 can be appropriately selected fromcommonly commercially available ones. For example, the resistor grid 14a composed of a thin film Cu—Ni is formed as a film on a resin film suchas a polyimide film. Furthermore, for example, the strain gauge 14 is afilm that is thin to the degree that the flexibility of the resin plate11 is not affected.

FIG. 4 is a circuit diagram (wiring diagram) showing an example of abridge circuit configured to measure a variation in the resistance ofthe strain gauge 14. The bridge circuit is of a Wheatstone type widelyused to measure a variation in the resistance of the strain gauge 14. Inresponse to an appropriate input voltage P, the bridge circuit outputsan output voltage 19 through a gain amplifier 18. For example, for thestrain gauge 14, resistors R1 and R2 have a resistance value of about100Ω, and a resistor R3 is used as a variable resistance.

FIG. 5 is a diagram schematically showing an example of a scanning Hallprobe microscope comprising the magnetic sensor 1 shown in FIGS. 1 to 4as an embodiment of a scanning microscope according to the presentinvention. A scanning Hall probe microscope 100 comprises a drivingmechanism 20 (driving means) in which the upper end, in FIG. 5, of amovable shaft 22 with a holder 21 provided at the lower end thereof, inFIG. 5, is connected to a stepping motor 23. The base 13 of the magneticsensor 1 is fixedly supported on an area of the holder 21 which isslightly inclined forward and downward, for example, at threadedportions 13 a shown in FIG. 2. Thus, the magnetic sensor 1 as a whole isthree-dimensionally driven, together with the holder 21 and the movableshaft 22, in an X direction, a Y direction, and a Z direction by thestepping motor 23. In this manner, the scanning Hall probe microscope100 comprises no actuator of a piezoelectric element type that uses apiezoelectric element as driving means.

Furthermore, the gauge lead 17 of the strain gauge 14 is connected to acontrol circuit section 30 (control means) in which the bridge circuitshown in FIG. 4 described above is contained. The stepping motor 23 isconnected to the control circuit section 30 via an I/O interface. On theother hand, the wires 16 connected the Hall element section 12 and drawnout via the terminals 16 b on the base 13 are connected to a measurementcircuit section 40. The control circuit section 30 and an imageprocessing operation circuit 50 are connected to the measurement circuitsection 40 via respective I/O interfaces.

To allow the magnetic domains of the surface Sa of the measurementsample S to be observed using the scanning Hall probe microscope 100configured as described above, for example, the following procedure iscarried out. That is, a balanced output voltage from the bridge circuitof the control circuit section 30 with the strain gauge 14 connectedthereto is adjusted to zero (step 1). Then, with the balanced outputvoltage from the bridge circuit of the control circuit section 30monitored, the stepping motor 23 is actuated to drive the movable shaft22 in the Z direction (which is perpendicular to the surface Sa of themeasurement sample S). Micromotion control is then performed togradually lower the magnetic sensor 1 toward the surface Sa of themeasurement sample S (step 2).

When the Hall element section 12 of the magnetic sensor 1 comes intoabutting contact with the surface Sa of the measurement sample S, theresin plate 11 bows so as to be recessed. Thus, the strain gauge 14installed on the resin plate 11 similarly bows. Then, the resistor grid14 a of the strain gauge 14 is deformed and expanded or contracted tochange the electric resistance thereof. The bridge circuit outputs acorresponding voltage signal (the balanced voltage deviates from zero).At this time, the control circuit section 30 provides a control signalto instantaneously stop driving of the stepping motor 23 (step 3). Then,with the Hall element section 12 of the magnetic sensor 1 maintained inabutting contact with the surface Sa of the measurement sample S, thestepping motor 23 is actuated in the X-Y direction (the directionparallel to the surface Sa of the measurement sample S). Thus, themagnetic sensor 1 starts measuring magnetic domains (step 4: contactmode). A measurement signal from the magnetic sensor 1 is arithmeticallyprocessed by the measurement circuit section 40 and the image processingoperation circuit 50. For example, a visualized image of thedistribution of the magnetic domains is output to a monitor or the likeprovided in the image processing operation apparatus 50. The image isalso recorded in a recording medium or the like.

Alternatively, if the bridge circuit of the control circuit section 30outputs a voltage signal, the operation direction of the stepping motor23 is switched to raise the magnetic sensor 1 from the current positionthereof. When the voltage output from the bridge circuit of the controlcircuit section 30 is zeroed again, the driving of the stepping motor 23is instantaneously stopped (step 3′). The currently available steppingmotor 23 can perform control such that the magnetic sensor 1 is stoppedat an appropriate position to an accuracy of about 100 nm. Thus, themagnetic sensor 1 is positioned slightly above the surface Sa of themeasurement sample S. That is, the magnetic sensor 1 is positioned inclose proximity to the surface Sa of the measurement sample S but not incontact with the surface Sa (non-contact state). Thereafter, with thisstate maintained, the above-described step 4 can be carried out(non-contact mode) to observe the magnetic domains of the measurementsample S. As described above, the control circuit section 30 may controlthe driving mechanism 20 so that the Hall element section 12 and themeasurement sample S are adjustably brought into abutting contact witheach other or separated from each other, based on the output signal fromthe strain gauge 14.

FIGS. 6 to 8 show an example of a two-dimensionally visualized imageobtained by measuring the magnetic domains in a 50 μm×50 μm area on thesurface of a thin iron garnet film of thickness 50 μm using an apparatusconfigured similarly to that of the scanning Hall probe microscope 100.FIGS. 6 to 8 show the results of scanning with the magnetic sensor 1positioned in contact with the measurement sample (contact mode), theresults of scanning with the magnetic sensor 1 positioned about 0.5 μmabove the measurement sample (non-contact mode), and the results ofscanning with the magnetic sensor 1 positioned about 1 μm above themeasurement sample (non-contact mode), respectively.

In the measurement, the specified characteristics of the magnetic sensor1 were such that the room-temperature electron mobility and sheetcarrier concentration of two-dimensional electron gas (2DEG) induced bythe heterojunction of the Hall element section 12 were 6,900 cm²/Vs and3.1×10¹² cm⁻², respectively, and that the Hall coefficient and seriesresistance of the sensor 1 were 0.001 Ω/G and 7.0 kΩ, respectively.Furthermore, the driving current for the Hall element section 12 wasconstantly set to 40 μA. Additionally, in the present measurement, thesurface magnetic field of the measurement sample varied by ±212 G. Theresults indicate that in the contact mode, magnetic distribution imagesare obtained which exhibit higher sensitivity and higher definition thanin the non-contact mode.

As described above, the magnetic sensor 1 and scanning Hall probemicroscope 100 according to the present invention enable the magneticdomains to be observed without using an AFM probe that utilize a tunnelcurrent. Thus, the magnetic sensor 1 and scanning Hall probe microscope100 can be applied to technical fields such as the magnetic measurementnot only of conductive materials but also of nonconductive materials,for example, magnetic measurement for detecting Hall-like defects innonmagnetic metal piping. Furthermore, no actuator using a piezoelectricelement is required to drive the magnetic sensor 1. Consequently, theapparatus configuration of the scanning Hall probe microscope 100 can besimplified. Additionally, the scan range at very low temperature can besufficiently increased, enabling magnetic measurement over a wiretemperature range. Moreover, sensitive magnetic detection can beachieved with the magnetic sensor in contact with or in close proximityto the measurement sample. As a result, the magnetic measurementperformance and reliability of the sensor and apparatus can bedrastically improved.

Note that, as described above, the present invention is not limited tothe above-described embodiments. The embodiments can be appropriatelyvaried without departing from the spirit of the present invention. Forexample, instead of the Hall element section 12, a magnetoresistivesensor that uses a magnetic resistor probe may be used as the magneticsensor 1. Furthermore, in the magnetic sensor 1, the Hall elementsection 12 need not necessarily be covered with a protective film.Moreover, if the pressure at which the Hall element section 12 is inabutting contact with the measurement sample S can be sensed based onthe amount by which the flexible resin plate 11 bows, that is, a strainamount signal from the strain gauge 14, then the stepping motor 23 maybe drivingly controlled such that the appropriate abutting contactpressure is maintained during scanning. Moreover, the measurement sampleS may be driven by the driving mechanism 20 with the magnetic sensor 1fixed.

As described above, the magnetic sensor and scanning microscopeaccording to the preset invention are very simply configured to allownot only conductive materials but also nonconductive materials to bemagnetically sensitively measured over a wide temperature range. Thus,the magnetic sensor and scanning microscope according to the presetinvention can be widely utilized in various magnetic measurementdevices, apparatuses, systems, facilities, and the like as well as themanufacture thereof.

1. A magnetic sensor comprising: a flexible member; a magnetic sensingelement disposed on the flexible member and configured to provide ameasurement signal representing one or more magnetic domains of asample; and a resistor grid disposed on the flexible member andconfigured to provide a variation in resistance representing adeformation of the flexible member.
 2. The magnetic sensor of claim 1,wherein the flexible member comprises a resin.
 3. The magnetic sensor ofclaim 2, wherein the resin is a polyimide resin film
 4. The magneticsensor of claim 1, wherein the magnetic sensing element is configured toprovide the measurement signal when disposed in abutting contact withthe sample.
 5. The magnetic sensor of claim 1, wherein the magneticsensing element comprises a Hall element or a magnetoresistive element.6. The magnetic sensor of claim 1, wherein the magnetic sensing elementis coated with a protective film.
 7. The magnetic sensor of claim 6,wherein the protective film has a thickness of about 50 nm.
 8. Themagnetic sensor of claim 6, wherein the protective film comprises anorganic nitride or silicon nitride.
 9. The magnetic sensor of claim 1,wherein the resistor grid comprises a thin film of Cu—Ni.
 10. Themagnetic sensor of claim 1, further comprising: a circuit in electricalcommunication with the resistor grid and configured to measure thevariation in resistance provided by the resistor grid.
 11. The magneticsensor of claim 10, wherein the circuit is further configured todetermine when the magnetic sensing element is in abutting contact withthe sample based on the variation in resistance provided by the resistorgrid.
 12. The magnetic sensor of claim 1, further comprising: ameasurement circuit section operably coupled to the magnetic sensingelement and configured to process the measurement signal from themagnetic sensing element.
 13. The magnetic sensor of claim 1, furthercomprising: an image processing operation circuit operably coupled tothe magnetic sensing element and configured to provide an image of theone or more magnetic domains in the sample based on the measurementsignal.
 14. The magnetic sensor of claim 13, further comprising: amonitor operably coupled to the image processing operation circuit andconfigured to display the image of the one or more magnetic domains inthe sample.
 15. The magnetic sensor of claim 13, further comprising: arecording medium operably coupled the image processing operation circuitand configured to record the image of the one or more magnetic domainsin the sample.
 16. A method of measuring one or more magnetic domains ina sample, the method comprising: providing a magnetic sensing elementand a resistor grid on a flexible member; measuring a variation in aresistance of the resistor grid caused by deformation of the flexiblemember; determining whether the magnetic sensing element is in abuttingcontact with the sample based on the variation in resistance; andmeasuring the one or more magnetic domains in the sample with themagnetic sensing element.
 17. The method of claim 17, furthercomprising: processing the measurement signal from the magnetic sensingelement.
 18. The method of claim 17, further comprising: providing animage of the one or more magnetic domains in the sample based on themeasurement signal.
 19. The method of claim 18, further comprising:displaying the image of the one or more magnetic domains in the sample.20. The method of claim 18, further comprising: recording the image ofthe one or more magnetic domains in the sample.
 21. A magnetic sensorcomprising: a flexible member; a magnetic sensing element disposed onthe flexible member and configured to provide a measurement signalrepresenting a magnetic domain of a sample; a resistor grid disposed onthe flexible member and configured to provide a variation in resistancerepresenting deformation of the flexible member; a circuit in electricalcommunication with the resistor grid and configured to determine whenthe magnetic sensing element is in abutting contact with the samplebased on the variation in resistance provided by the resistor grid; anda measurement circuit section operably coupled to the magnetic sensingelement and configured to process the measurement signal from themagnetic sensing element.
 22. The magnetic sensor of claim 21, furthercomprising: an image processing operation circuit operably coupled tothe magnetic sensing element and configured to provide an image ofmagnetic domains in the sample.